Cellular communications networks continue to experience rapid growth, with the volume of data traffic in mobile broadband in particular increasing exponentially. Unlike in the early days of mobile telephony, over 70% of cellular communication network usage today is indoor, and with the global population becoming increasingly urbanised, indoor cellular network use is also set to increase. The provision of consistent and reliable indoor network coverage via conventional macro cells is inherently challenging, and when investigating those users whom macro cells have difficulties serving, it can be found that almost 100% of such “problem” users in urban areas are located indoors.
The primary network solution for providing reliable indoor network coverage is the deployment of Low Power Nodes (LPNs), including small cells and Distributed Antenna System (DAS) networks. LPNs transmit at signal power levels that are considerably lower than those used in macro cells, and are physically much smaller. LPNs are therefore deployed within indoor environments to provide network coverage in areas where macro cells are unable to meet network demand. Small cells, including for example micro, pico and femto cells, are typically used in an ad hoc deployment to provide coverage and/or capacity extension in relatively small areas. Small cells usually support a single wireless technology and carrier, and provide a relatively immediate solution to small scale capacity or coverage problems.
DAS networks may represent a larger investment, both financially and in the planning and design of their deployment, however DAS networks offer a more robust, flexible and scalable solution for addressing a large range of coverage and capacity issues in indoor/semi-indoor environments. DAS networks can accommodate multiple frequencies and wireless technologies for different wireless carriers and are one of the primary solutions for network coverage in medium to large indoor environments.
FIGS. 1 and 2 illustrate an example DAS network configuration and deployment. Referring to FIG. 1, a DAS network 2 comprises an indoor hub 4 having a backhaul connection to a macro network cell (not shown). Within the hub is located a Digital Unit 6 providing centralised digital baseband and an Indoor Radio Unit 8. The hub 4 may support multiple Active Antenna Elements (AAEs), also known as Active Antenna Heads or Radio Heads (RHs) 10 which have a wired connection to the IRU of the hub and transmit and receive radio signals. In some deployments, as shown in FIG. 2, the IRU 8 of the hub 4 may be distributed as multiple IRUs 8 deployed on individual floors or in individual segments of a building, each distributed IRU 8 supporting multiple AAEs 10. In very large venues or campuses, centralised baseband may also be shared over multiple Digital Units 6, each cooperating with multiple IRUs and with each IRU supporting multiple AAEs.
A DAS network as illustrated in FIGS. 1 and 2 may comprise many tens of thousands of AAEs deployed across multiple floors of multiple buildings. Managing such large DAS networks to ensure service provision in a cost effective manner while ensuring compliance with customer Service Level Agreements (SLAs) is a complicated task. Typically, when a fault is reported on an AAE, an alarm is received by the network management function of the DAS network operator. The network management function will then arrange for the faulty AAE to be replaced through its standard repair and service fulfillment procedures. This will generally involve arranging access to the building where the AAE is located and scheduling a visit from appropriate personnel to replace the AAE. During this time, the AAE will remain out of service, reducing the network coverage and capacity offered by the DAS network.
AAEs have a finite operating lifetime, meaning that hardware upgrades and hardware failures are a part of normal business operations. As the scale and complexity of a DAS network increases, with large volumes of antenna heads located in different buildings over multiple floors, possibly supporting multiple customers with differently tailored SLAs, the task of managing equipment lifecycle while meeting SLAs and maintaining operating expenses at an acceptable level becomes increasingly challenging.